A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with carbon atom having three covalent bonds, and it bears a +1 formal charge. But IUPAC confuses coordination number with valence, incorrectly considering carbon in carbenium as trivalent.[1]
In older literature the name carbonium ion was used for this class, but now it refers exclusively to another family of carbocations, the carbonium ions, where the charged carbon is incorrectly considered pentavalent by the IUPAC,[1] but it is pentacoordinated, not pentavalent, because the coordination number and valence are two different things. The current definitions were proposed by the chemist George Andrew Olah in 1972,[2] and are now widely accepted.
Carbenium ions are generally highly reactive due to having an incomplete octet of electrons; however, certain carbenium ions, such as the tropylium ion, are relatively stable due to the positive charge being delocalised between the carbon atoms.
^ abIUPAC Gold Book carbonium ion
^"Stable carbocations. CXVIII. General concept and structure of carbocations based on differentiation of trivalent (classical) carbenium ions from three-center bound penta- of tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions" George Andrew Olah; J. Am. Chem. Soc.; 1972; 94(3); 808–820.
A carbeniumion is a positive ion with the structure RR′R″C+, that is, a chemical species with carbon atom having three covalent bonds, and it bears a...
studied. The carbonium ion has a planar geometry. In older literature, the name "carbonium ion" was used for what is today called carbenium. The current definitions...
to the ease of measuring the disappearance of the carbeniumion absorbance. Common carbeniumions are trityl and tropylium cations. Ionizing radiation...
carbon: three in the carbeniumions and five in the carbonium ions. This nomenclature was proposed by G. A. Olah. Carbonium ions, as originally defined...
oxygen atoms. An oxocarbenium ion is represented by two limiting resonance structures, one in the form of a carbeniumion with the positive charge on carbon...
A polyatomic ion (also known as a molecular ion) is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave...
differentiation of trivalent (classical) carbeniumions from three-center bound penta- or tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic...
from ammonia (NH3). Fluxional methanium can be visualised as a CH+3 carbeniumion with a molecule of hydrogen interacting with the empty orbital in a...
do not contain the cation. Triphenylcarbenium is a relatively stable carbeniumion, because the positive charge is partially distributed among 10 of the...
carbocation and an enium ion, making it the simplest of the carbeniumions. Experiments and calculations generally agree that the methenium ion is planar, with...
reaction, since the carbon atom is converted into an sp2 hybridized carbeniumion during the transition state for the rate-determining step with an increase...
having alternating single and multiple bonds. Lone pairs, radicals or carbeniumions may be part of the system, which may be cyclic, acyclic, linear or mixed...
ethylacetoacetate 1 and the aryl aldehyde is the rate-limiting step leading to the carbeniumion 2. The nucleophilic addition of urea gives the intermediate 4, which...
the decay technique for preparing and studying organic radicals and carbeniumions. In a variant of that technique, exotic species like methanium are produced...
appear when the Br− is large excess in the reaction medium. A β-bromo carbeniumion intermediate may be predominant instead of 3 if the alkene has a cation-stabilizing...
The Bamford-Stevens reaction gives carbenes in aprotic solvents and carbeniumions in protic ones. The different mechanisms imply that singlet carbene...
cyclization reactions and because it is possible to capture the oxo-carbeniumion with a large array of nucleophiles. The halo-Prins reaction is one such...
Hogeveen showed that 2HF·SbF5 reacts with isobutane and neopentane to form carbeniumions: (CH3)3CH + H+ → (CH3)3C+ + H2 (CH3)4C + H+ → (CH3)3C+ + CH4 It is also...
ions such as iminium and nitrilium. A simple onium ion has a charge of +1. A larger ion that has two onium ion subgroups is called a double onium ion...
family of carbeniumions, with three fluorine atoms as substituents in place of its hydrogen atoms. Compared to methenium (the simplest carbeniumion), trifluoromethyl...
"Transition metal-stabilized carbeniumions as synthetic intermediates. I. α-[(alkynyl)dicobalt hexacarbonyl] carbeniumions as propargylating agents"....
usual four bonds to Si, silylium ions are the silicon analogues of carbeniumions. They can be viewed as protonated silylenes. Early efforts to generate...
"Transition metal-stabilized carbeniumions as synthetic intermediates. I. α-[(alkynyl)dicobalt hexacarbonyl] carbeniumions as propargylating agents",...
observed due to fragmentation and dimerization of carbon monoxide-derived carbeniumions, especially since each step of the reaction is reversible. Alkyl sulfuric...
Global Information